Effect of a Bacterial Consortium on the Mechanical and Durability Properties of Self-Healing Concrete at Different Water–Cement Ratios

Concrete, when used in construction, is prone to internal micro cracks that compromise its strength, flexibility, durability and lifespan. To address this, self-healing concrete technologies using microbial-induced calcium carbonate precipitation (MICP) have gained significant attention. The objective of this study was to focus on the preparation of a bacterial consortium (BV) composed of Bacillus cereus and Vibrio natriegens, selected for their specific characteristics to produce calcium carbonate under alkaline conditions. These bacterial strains with nutrients were added in optimised proportions to the concrete mixes and evaluated their healing potential. The effectiveness of the bacterial consortium on the self-healing potential of concrete was investigated. Similarly, the performance of this consortium was assessed across three different water–cement (w/c) ratios: 0.40, 0.45, and 0.50. These variations were selected to investigate the influence of moisture availability and mixed porosity on bacterial activation and crack healing efficiency. Mechanical tests like flexural strength, split tensile strength and compressive strength were performed to assess the structural recovery. Durability tests such as acid resistance, water absorption, and non-destructive tests like ultrasonic pulse velocity were also performed. Based on these investigations, a 0.40 w/c ratio of bacterial consortia (0.40 BV) showed the best performance. These results indicate that the bacterial consortium can significantly improve the self-healing properties of concrete, particularly at low w/c ratios.